alternative for onbeforeunload for Chrome

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Javascript

Is there any alternative for onbeforeunload for Chrome..here is my code

window.onbeforeunload = CloseSession;

function CloseSession() {
//log out the user from demand if browser close or alt+f4 is pressed not for back button
if ((window.event.clientY < 0) && (window.event.clientX > 40) ||
(event.altKey == true && event.keyCode == 0))
window.open('LogOffUser.aspx', '_parent', 'left = 9999, top = 9999,width=1px,height=1px');
}